CHICAGO: A common virus caused human adult stem cells to turn into fat cells and could explain why some people become obese, US experts said on Monday.

The research builds on prior studies of adenovirus-36 - a common cause of respiratory and eye infections - and it may lead to an obesity vaccine, they said.

"We're not talking about preventing all types of obesity, but if it is caused by this virus in humans, we want a vaccine to prevent this," said Nikhil Dhurandhar, of Pennington Biomedical Research Centre at Louisiana State University System.

The virus adenovirus-36 or Ad-36, caused animals to pack on the pounds in lab experiments. "These animals accumulated a lot of fat," Dhurandhar said.

Dhurandhar also has shown that obese people were three times more likely to have been infected with Ad-36 than thin people in a large study of humans.

Now, researchers in Dhurandhar's lab have shown that exposure to the virus caused adult human stem cells to turn into fat-storing cells.

Magdalena Pasarica, who led the study, obtained adult stem cells from fat tissue of people who had undergone liposuction.

Stem cells are a type of master cell that exist in an immature form and give rise to more specialised cells.